Device and method for adjusting components in an extrusion tool

Abstract

The invention relates to a device for producing plastics tubes by extrusion, comprising an extruder (1), an extrusion tool (2), which adjoins the extruder in the production direction and consists of a main tool and a shaping die insert, which adjoins the main tool and comprises at least a bushing (10) and a mandrel (11), wherein a melt channel (9) with a circular outlet gap (18) is formed between the mandrel (11) and the bushing (10), the bushing (10) being adjustable relative to the mandrel (11). According to the invention, it is provided that there is an adjustment element (12), which is operatively connected to the bushing (10) and can be adjusted via at least one drive (14), the adjustment element (12) being in contact with a sliding block (19) having a spherical sliding surface (17). The invention also relates to a corresponding method for adjusting the bushing (10).

Description

[0001] Device and method for adjusting components in an extrusion tool

[0002] Description:

[0003] The invention relates to a device for producing plastic pipes by extrusion, comprising an extruder and an extrusion die connected to the extruder in the direction of production, consisting of a base die, a subsequent shaping die insert with at least one sleeve and a mandrel, wherein a melt channel with a circular outlet gap is formed between the mandrel and the sleeve, wherein the sleeve is adjustable relative to the mandrel. Furthermore, the invention relates to a related method for adjusting the sleeve.

[0004] A sleeve-and-dome pipe extrusion die is a device used to produce plastic pipes. The basic principle is that a molten plastic is forced through a melt channel, with the sleeve and dome forming an exit annular gap that approximately replicates the desired pipe shape.

[0005] The process begins with feeding plastic pellets or melt into an extrusion machine. The machine melts the plastic and forces it through a screw or piston into the sleeve. The sleeve has an opening approximately the shape of the desired tube.

[0006] The molten plastic is forced through the sleeve by pressure caused by frictional forces. At the same time, the mandrel is inserted into the interior of the sleeve to form the hollow space of the tube. The mandrel is shaped like the interior of the tube and ensures that the plastic takes on the correct shape.

[0007] The basic principle of the sleeve-and-mandrel pipe extrusion die enables the production of plastic pipes in various sizes and shapes. It is an efficient process that allows for the continuous production of large quantities of pipes in a short period of time. The mandrel can be moved within the sleeve. This allows for the production of pipes with different diameters or wall thicknesses. By moving the mandrel, the distance between the mandrel and the sleeve can be changed, which in turn affects the size of the pipe's cavity. The exact adjustment of the mandrel depends on the specific requirements of the pipe being produced. This enables flexible production and adaptation to diverse customer requirements.

[0008] The centering of the sleeve relative to the mandrel can be changed to adjust the properties of the extruded pipe. A centering of the mandrel results in a uniform wall thickness, while a shift of the sleeve relative to the mandrel can lead to an uneven wall thickness. Changing the centering can be achieved using special tools. It is important to consider the effects of such a change on the quality and properties of the extruded pipe. This can be particularly relevant when the so-called "sagging effect" occurs. The sagging effect occurs when the wall thickness of the extruded pipe is uneven, resulting in bulging or sagging of the pipe wall. Changing the centering of the sleeve relative to the mandrel can help counteract the "sagging effect."

[0009] By deliberately shifting the sleeve relative to the mandrel, the wall thickness of the tube can be made more uniform. A central position of the mandrel results in a uniform wall thickness, while shifting it can lead to a targeted adjustment of the wall thickness in specific locations.

[0010] By changing the centric position of the mandrel to the sleeve, the sacking effect can be minimized or avoided by achieving a more uniform wall thickness of the extruded tube.

[0011] Some extrusion dies feature an electric motorized adjustment system, which can adjust the melt gap and thus increase or decrease the exit gap evenly across the entire circumference. Manual centering screws allow the melt exit to be increased in one spot and then naturally decreased in the opposite spot.

[0012] The object of the invention is to provide a device and a method by means of which the sleeve can be adjusted in its position relative to the mandrel from outside the tool in order to be able to adapt the exit gap to given requirements.

[0013] The solution to the problem is characterized in conjunction with the preamble of claim 1 in that an adjusting element is arranged which is operatively connected to the sleeve and is adjustable via at least one drive, wherein the adjusting element is in contact with a sliding block with a spherical sliding surface.

[0014] The drive moves the adjusting element on the sliding block and thus brings the sleeve into a different position relative to the mandrel, thereby changing the circular exit gap.

[0015] According to a further development, a bolt is arranged between the drive and the adjustment element. The drive then initially moves the bolt, usually along an axis equidistant from the extrusion axis, and then moves the adjustment element and thus the sleeve relative to the mandrel.

[0016] According to a further development, a spring pack is provided for preloading the adjustment element. The spring pack, preferably a number of disc springs arranged one behind the other, is preloaded by a component, for example, a hexagon socket screw, thus bringing the adjustment element, sliding surface, etc., into an initial position in which the naturally occurring play between the moving parts is largely eliminated. This achieves a melt-tight seal between the adjustment element and the sliding block.

[0017] By means of the drive, the adjusting element, and thus the sleeve, is moved or tilted around the ball center of the sliding block along the spherical sliding surface. This design of the device allows the sleeve to be moved three-dimensionally around this point, thus adjusting the outlet gap to meet the requirements of the desired pipe cross-section.

[0018] According to the development, the drive is an electromechanical drive, such as a linear actuator or, in particular, a screw jack. Screw jacks, in particular, offer a high reduction ratio in a very compact installation space. Only a small drive power is required and they are very precise, as minimal adjustment steps of 0.05 mm are possible. Furthermore, very high adjustment forces of > 10 tons are possible.

[0019] The machine controls can precisely display the current position or travel of the drive. A relatively simple calculation can thus determine how the sleeve was moved from its initial position by the drive or actuators. If the sleeve adjustment is known, the geometry of the exit gap can also be determined. When the sleeve is moved toward the mandrel, the circular cross-section with the same wall thickness becomes a cross-section with different wall thicknesses. These reproducible settings make it possible to specifically influence the pipe being produced.

[0020] The solution to the method is characterized in conjunction with the preamble of claim 7 in that an adjusting element is moved along a spherical sliding surface of a sliding block, wherein a drive presses directly or indirectly against the adjusting element.

[0021] As already explained above, the drive moves the adjustment element and thus the sleeve in relation to the mandrel.

[0022] Further advantageous developments are set out in subclaims 8 to 10.

[0023] The proposed invention makes it possible to adjust the sleeve in a nozzle insert to the mandrel from the outside, wherein the adjustment is carried out from an initial position and the adjustment made is known and reproducible.

[0024] This has the advantage that, particularly in extrusion systems with predominant wall thickness measurement, it is possible to set up a control loop or create it using mathematical models and use this to react to changes during the ongoing process and to adjust the sleeve to the mandrel so that the desired wall thickness is achieved again in order to ensure the consistent quality of the plastic pipe.

[0025] The drawings show schematically a device according to the invention:

[0026] Fig. 1 shows a typical extrusion line

[0027] Fig. 2 a section through an extrusion tool with adjusted sleeve

[0028] Fig. 3 a section through an extrusion tool without adjusted sleeve

[0029] Fig. 4 schematically shows the centric position of sleeve to mandrel

[0030] Fig. 5 schematically shows the concentric position of sleeve to mandrel Fig. 6 schematically shows the position of sleeve and mandrel in three-dimensional space Fig. 7 an isometric view of the extrusion tool

[0031] Figure 1 shows a typical extrusion line used today for profile extrusion, whether for the production of window profiles or pipes. It shows an extruder 1 in which plastic is melted and continuously fed into the extrusion die 2 for shaping. This is followed by a calibration and cooling station 3; depending on the profile, additional cooling stations can be used. Following the cooling stations is a haul-off device 4. A cutting device 5 is arranged to cut the continuous profiles 6 to the desired length. The extrusion axis is marked with the number 7, and the extrusion direction with the number 8.

[0032] Figure 2 shows a section through an extrusion die 2 with a nozzle insert consisting of at least one sleeve 10 and a mandrel 11. A melt channel 9 is created between the inner contour of the sleeve 10 and the outer contour of the mandrel 11, forming an exit gap 18 at the exit of the extrusion die 2. In this exemplary embodiment, the sleeve 10 is moved upwards out of the extrusion axis 7, whereby the melt channel 9 is smaller in the lower region than in the upper region. The exit gap 18 thus no longer forms an annular cross-section. The movement of the sleeve 10 is achieved via the adjustment element 12, with which it is operatively connected. In this embodiment, drives 14 move the bolt 13 (the drive 14 can also act directly on the adjusting element 12), which in turn causes the adjusting element 12 to be moved along the spherical sliding surface 17 of the sliding block 19 and thus tilts the sleeve 10.The fact that the sliding surface 17 is a spherical cap, which results in a circle in a cross-section through a sphere, is indicated by the thick, dotted line. The extrusion direction is indicated by position number 8.

[0033] Figure 3 also shows the extrusion tool 2 according to Figure 2. Here, however, the sleeve 10 is not tilted towards the mandrel 11. Sleeve 10 and mandrel 11 are centrally located to one another, whereby the exit gap 18 is formed as a ring cross-section. Mandrel 11 and sleeve 10 assume a baseline starting position, which can be regarded as the basic setting. In this exemplary embodiment, spring assemblies 15 are arranged in the adjusting element 12 - other arrangements are conceivable - which hold the adjusting element 12 in this starting position. Any existing play, especially between the adjusting element 12 and the sliding block 19, is eliminated by the spring tension. The preload is selected such that sliding of the adjusting element 12 is still ensured, but the spherical sliding surface 17 is thus melt-tight. The springs in the spring assembly 15 can be adjusted via a preload component 16.In this embodiment, the preloading components 16 are standard hexagon socket screws, but other elements can also be used. The spring assembly 15 consists of a plurality of staggered disc springs. Identical positions are designated with the same position numbers.

[0034] Figures 4 and 5 show a schematic diagram of the position of mandrel 11 relative to sleeve 10. In Figure 4, mandrel 11 and sleeve 10 are arranged centrally, whereby the melt channel 9 and the outlet gap 18 form a circular ring, respectively, and have the same wall thickness. In the schematic diagram of Figure 5, the sleeve 10 is moved upward and thus shown eccentrically, shifting it from its concentric position. The central position is shown as a dashed line for comparison.

[0035] Due to the spherical sliding surface 17, adjustment of the sleeve 10 relative to the mandrel 11 is not only possible within a single plane; the sleeve 10 can be pivoted three-dimensionally in space around the center point 22 of the spherical sliding surface 17. Figure 6 shows a three-dimensional crosshair with the x, y, and z axes for clarity. The Z axis corresponds to the extrusion axis 8, and the center axis of the mandrel 11 is schematically represented as arrow 20. Arrow 21 schematically represents the center axis of the sleeve 10, which is pivoted around the center point 22 of the spherical sliding surface 17, which is pivoted not only on the Z plane in the X direction, but also from the Z plane in the Y direction.

[0036] Figure 7 shows a perspective view of the extrusion tool 2 with the extrusion direction 8. The electromechanical drives 14, four of which are shown in the exemplary embodiment, are used. For three-dimensional adjustment along the spherical sliding surfaces 17, even three of the drives 14 would be sufficient. If the drives can pull and push, even two drives would be sufficient. As already described, the drives 14 here cause the bolts 13 to be moved, which in turn rotate the adjustment element 12 about the center point 22 of the spherical sliding surface 17 of the sliding block 19, which in turn causes the sleeve 10 to be adjusted relative to the mandrel 11, thereby changing the geometry of the exit gap 18 of the melt channel 9.

[0037] The extrusion tool 2 thus comprises an electromechanical centering device according to the invention. This has the advantage that no personnel are required for manual centering. The operator can see the exact centering position on the control panel of the system control system, since the adjustment of the sleeve 10 is determined based on the movements performed by the electromechanical drives 14. Repeatable centering with high accuracy is thus possible. Programs for the centering position can also be created, enabling automatic centering with continuous wall thickness control.

[0038] List of reference symbols:

[0039] 1 extruder

[0040] 2 Extrusion tool

[0041] 3 Calibration and cooling station

[0042] 4 trigger device

[0043] 5 Separating device

[0044] 6 endless profile

[0045] 7 Extrusion axis

[0046] 8 Extrusion direction

[0047] 9 Melt channel

[0048] 10 sleeves

[0049] 11 Thorn

[0050] 12 Adjustment element

[0051] 13 bolts

[0052] 14 drive for 13

[0053] 15 spring pack

[0054] 16 Component for prestressing 15

[0055] 17 Sliding surface

[0056] 18 Exit slit

[0057] 19 Sliding block

[0058] 20 central axis of 11

[0059] 21 central axis of 10

[0060] 22 Sphere center x, y, z - crosshair

Claims

Patent claims:

1. Device for producing plastic pipes using the extrusion process, comprising an extruder (1), an extrusion tool (2) following the extruder in the direction of production, consisting of a base tool and a shaping nozzle insert following thereon with at least one sleeve (10) and a mandrel (11), a melt channel (9) with a circular outlet gap (18) being formed between the mandrel (11) and the sleeve (10), the sleeve (10) being adjustable relative to the mandrel (11), characterized in that an adjusting element (12) is arranged which is operatively connected to the sleeve (10) and is adjustable via at least one drive (14), the adjusting element (12) being in contact with a sliding block (19) having a spherical sliding surface (17).

2. Device according to claim 1, characterized in that a bolt (13) is arranged between the drive (14) and the adjusting element (12).

3. Device according to claim 1 or 2, characterized in that a spring assembly (15) is provided for pretensioning the adjusting element (12).

4. Device according to claim 1, 2 or 3, characterized in that by means of the drive (14) the adjusting element (12) and thus the sleeve (10) can be moved about a spherical center point (22) of the sliding block (19) with the spherical sliding surface (17).

5. Device according to at least one of the preceding claims, characterized in that the drive (14) is an electromechanical drive.

6. Device according to claim 5, characterized in that the drive (14) is a spindle lifting gear.

7. Method for adjusting a sleeve (10) in an extrusion tool (2), wherein the sleeve (10) is moved from the concentric position, wherein an outlet gap (18) at the end of the melt channel (9) is changed, characterized in that an adjusting element (12) is moved along a spherical sliding surface (17) of a sliding block (19), wherein a drive (14) presses directly or indirectly against the adjusting element (12).

8. Method according to claim 7, characterized in that the adjusting element (12) assumes a starting position with respect to the sliding block (19), this starting position is held by at least one arranged spring assembly (15), wherein the preload of the spring assembly (15) is adjusted by means of preloading components (16), wherein the preload is adjusted such that the adjusting element (12) can slide on the spherical sliding surface (17), wherein the preload is adjusted such that the spherical sliding surface (17) between the adjusting element (12) and the sliding block (19) is melt-tight.

9. Method according to at least one of claims 7 or 8, characterized in that the position of the sleeve (10) relative to the mandrel (11) is determined via the position of the drives (14) and the geometry of the outlet gap (18) is determined via this.

10. Method according to one of claims 7 to 9, characterized in that in conjunction with an automatic wall thickness measurement, a control loop is determined which continuously optimizes the wall thickness of a produced plastic pipe.

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